This application aims to study whether NO induced by cytokines can affect HIV-1 provirus synthesis. To accomplish this, the specific aims are to construct retroviral vectors which have inducible NO synthetase under tat regulation. In Aim 2, the application will analyze the effect of NO synthetase over-expression on HIV replication. In Aim 3, the application will examine the effect of NO on integrated HIV-1 provirus and HIV transcription in chronically-infected lines. Aim 4 is to determine the NO effect on the expression of IFN-a resistant HIV-1 isolates. These studies might lead to new therapies for HIV replication.